2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/53143In this letter we propose a new ansatz for the thermal string in the TFD formulation. From it, we derive the thermal vacuum for the closed bosonic string and calculate the thermal partition function in the blackhole $AdS$ background in the first order of the perturbative quantization.9 pages, latex fileHigh Energy Physics - Theorytext